Hermetic variable gap crystal holder



Jan 6, 1953 A. E. MILLER HERMETIC VARIABLE GAP CRYSTAL HOLDER Filed Feb. 26 1951 CIA/if for/1 ey Patented Jan. 6, 1953 ABLE GAP CRYSTAL HERMETIC VARI HOLDER August E. Miller, CliHside Park, N. J., assignor to the United States of America as represented by the Secretary of the Army Application February 26, 1951, Serial No. 212,765

(Cl. S10-9.3)

5 Claims.

The invention relates broadly to piezo-electric crystal apparatus, and more particularly to an improved construction of a piezo-electric crystal holder.

The invention is directed primarily to a crystal holder that is hermetically sealed and having fixed and movable electrodes, and a piezo-electric crystal of fixed frequency positioned between said electrodes whereby the frequency of the crystal can be varied within certain line limits by varying the air gap between the crystal and the movable electrode.

It is, accordingly, one of the objects of the present invention, to provide a piezo-electric crystal holder wherein the frequency of a particular crystal may be varied by providing means for varying the air gap between the crystal and the movable electrode.

Another object of the invention is to provide a crystal holder, wherein the crystal is hermetically sealed at all times, thereby providing for more stable operation of the device.

A still further object of the invention is to provide a piezo-electric crystal holder wherein actuation of the adjustable electrode is accomplished from a source external of the inner elements of the holder, thus assuring a completely hermetically sealed holder at all times.

For a clearer understanding of the nature of the invention and additional advantages, feaftures and objects thereof, reference is made to the following description, taken in connection with the accompanying drawing, in which,

Fig. 1 is a cross-sectional view of a crystal holder embodying the present invention,

Fig. 2 is an exploded view showing, in perspective, the several parts of the holder, and

Fig. 3 is a perspective view showing the inside of the cover plate and driver plug.

Referring to the drawing, the crystal holder comprises a housing consisting of a rectangular container II and a cover I3, the container II being composed of an insulating material, such as Bakelite, or thelike, while the cover plate I3 is preferably made of metal. The cover I3 is removably fastened to the container I I by screws I5, insertable through circular openings in the cover I3 and engaging corresponding openings of internally threaded sleeves I4 in the container I I.

For mechanically supporting and for establishing external electrical contacts for the holder, three tubular metal pins or prongs Il, i9 and 2| are provided, which are secured to the outside bottom surface of the holder. The wires 23 and 25 are provided to make the appropriate electrical connections to the prongs Il, 2l, as in conventional commercial practice. In the specific embodiment herein, wire 23 has its other end secured to a slightly arced contact plate Z3, preferably made of springy copper, which is immediately adjacent the back wall of the container. Wire 25 is similarly secured to the plate supporting the movable electrode which will be more fully described hereinafter. Lying Hush against the contact plate 29 is a xed Aelectrode 3l. Parallel to, and anteriorly positioned with respect to the xed electrode, is a supporting plate 33, for the movable electrode, the construction and function of which will be hereinafter described. The plate 33 is spaced from the fixed electrode 3l by tubular ceramic spacers 35 and further insulated from the xed electrode by ceramic insulators 3l. The insulators 31 are likewise tubular, each having a shank portion, which is insertable into a hole in plate 33, and a head portion which is slightly larger than the aforementioned hole of the plate. Four screws 39, insertable through both the insulators 31 and the spacers 35 and engageable in corresponding circular threaded openings in the xed electrode 3I, serve to fasten together the iixed and movable electrode fixture. Disposed in the space between the fixed electrode 3| and the plate 33 is a frame 4I having a substantially rectangular aperture 43 of a size to accommodate a piezoelectric crystal 45. To hold the crystal 45 in position, and complete the crystal sub-assembly, there is provided a flat retainer 4l, having a central aperture 48 and holes for the insertion of lock washers 49 and screws 50, which are insertable through corresponding holes in the rame 4I and threaded holes in the xed electrode The plate 33 is provided with a threaded central circular aperture 5I and further provided with a threaded hole 52 for accommodating the screw 54, which serves as a binding post for the wire 25. Within the aperture 5I, there is pcsitioned an externally threaded electrode 53 which, by virtue of such screw threaded surface. is adjustably movable in the plate 33.

As shown in Fig. 1, movable electrode E3 Y substantially cup-shaped and further provided with a central depressed portion 55. The entire forward lip or edge of the electrode is provided with teeth 5l, thereby forming a series of radial grooves about the entire edge of the electrode E3. Encircling and threadably engaging the movable electrode 53 is an internally threaded ring having a hole to accommodate a set screw 3 Whichjserves to retain or hold the electrode 53 rmly in :positionlwithin the, ring 5R Secured f to the upper portion of the front of the plate 33 is a friction lock BI, comprising essentially a flattened face portion that lies flush against the plate 33 and a perpendicularly extending springlike element 63 which resiliently engages the ring 58.

The cover plate I3 has a central aperture which is in substantial alignment withfthe cavityof the movable electrode 53. Bonded tothe'cover plate I3, and confined Within the aperture of said plate is a resilient rubber ring |55.v Extending through the opening of the ring 65, and similarly bonded thereto, is a metallic drivel` plug 61. Theoutside, ,or exposed, face of the driver plug isprovided with avchannel orkerfffor accommodating a screw driver or similar instrument. lfhe inner face-of the-driver plugl `comprises a substan- Ltially nat plate or ,diskl II of a diameter slightly Alargerrthan *that of` the. movable electrode 53.

Rising. from the face ofthe diskfII areknife-edge ridges 'I3 thatfa're always in alignment with any one'lpairfof opposite :grooves'fof the movable elec- !tmdefsa. Imate u is also provided Waagen-tial l'depression 1,5whichQ-Scrvesas av receptacle for one-'end of-a coilspring. 71,. The other, end of the springfllrests within the depre`s"s`edk portion Hof the-movable .electrode 53;;A To insure an kair- .f vtight seal-,1v provide,- Ja rublber. gasket 79 between tithe cover I13-and-th'e container I I.

In operation, av-sorewdriver'or similarK instrufment is'inserted into the kerf69 of the driver 'plugl -The :plug canthenfbe depressed, vrcausing theknife-edge ridge .13. to-.mesh vwith or engage grooves inf V the adjustable electrode 5 3., QSli'ght movement, eitherclockwise'tlor counteroloclgwse vof the-'screwv driven will .then iect' a slight axial movement of the adjustable electrode tdvagryjgthe "'fairgap betweenrthecrystal and movablefelectrode as desired.` The screw-driver. is thenrwithdrawn, rvand the ,-resiliencyf-M1 -the rubber' ring; aided by the action,` of the spring 'I.'I,'` willV force' the j plug :back Ato Aits original positionj vvh'e're the' 'operation can =be fr epeatedas oftenasrequiredgtolsetjthe n adjustable; electrode in any desired position relaytiveto-thexedelectro'da To prevent ,any acci- Y; dental or inadvertent: movement of? th movable "'e1ectrode.1the lool;A 6 I is utilized'wherein` spring .*actionoffelement 63 will resista/ny .movement of `ring58ffrom its-desiredposition. "Q

While there Ihas been described 'one specilic embodiment of the invention, it is orbvious that modifications andhangesrnay be made without de- -;part i ngfro1n the spirit and scope of the 'inventnaa de@ ed Y by accompanying claims. :Whatrsplaimedisl A L vAiahermeticallv sealed, adjfstabie air' gap L, piezorelectricg'crystal holder comprising a vcontainer and a cover plate therefor, a xed electrode within said container and a substantially cupshaped movable electrode comprising a cylindrical housing terminating at one end in a iiat base and its other end in a rim having radially dis- 4 posed teeth, said base being spaced from and substantially parallel to said Xed electrode, a piezoelectridcrystal positioned between said fixed and movable electrodes, and means ,onsaid cover plate for engaging the teeth on the rim of said movable electrode and electing rotational movement thereof.

L; 2: -A hermeti'cally sealed, adjustable air gap piezo-electric crystal holder comprising a container and 'a cover plate therefor, a fixed electrode Ewitliinsaid container and a movable electrode "spaced-from said'lxed electrode, a piezo-electric crystal A,positioned between said fixed and movable tatableV "screwV f threaded :electrode: having A,en-

gageablefmeansrthereon and spaced -froin said xed electrode, a piezo-electric crystalb'etween said xedand' rotatable electrodes,i a resilient diaphragm secured to the periphery ofV said aperture-'and means 'secured t0; VSaid diaphragm. for engaging said' engageable means of-safdrotatable electrode for eiecting rrotational movement `tl'lereoff E "7 r" 4. An hermetically sealed-inolosure .for ian eleo- V"tric device `havingai'ixed electrode-anda rotatable sorew"thr'eade`d electrode mounted, in-said inolosure, comprising a container and -amaperturedv cover therefor, a resilient diaphragm secured to 'the peripherypot-saidaperture: and means 'secured' to said resilient diaphragm. `for engaging and effecting rotational movement. of said rotatable electrodef l f,

5. An inclosureofV 'the type described in claim 'ejwher'ein themeans inusaid resilient diaphragm for engagingand'efecting movement of said rotatable electrode comprises a plate-likeplug secured to said -resilient diaphragm, said plug having a groove iniits outer;lac eand a knife-like ridge on its innerface.r ,i

AUGUSTE.

' "RIEERCESjCrrEn The following references are otrecojrd in the file of this :patent: i A' j UNITED vs'rATEs PATENTS"-v Number Name Date 1,619,125 Iloughj Mar. 1, 1927 ,LThoma's T gtjqlggg FOREIGN PATENTS Number Country Date 567,552 Germany Jan. 6, 1933 

